Fluorinated chemical compound



United States Patent 3,203,999 FLUORINATED CHEMICAL COMPOUND David Milton Gardner, North Wales, Pa., Robert Edward Oesterling, Silver Spring, Md., and Murray Hauptschein,

Glenside, Pa., assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed June 28, 1962, Ser. No. 207,157

1 Claim. (Cl. 260633) This invention relates to the new compound 2,2- dilluoro-Z-nitroethanol, particularly useful as a stable monopropellant for rocket propulsion.

The desired characteristics for a high performance monopropellant are high specific impulse, high thermal stability, good storage stability and ease of handling. The specific impulse value is a measure of the total thrust available from a given weight of propellant. (See Rocket Propulsion Element-s, George P. Sutton, John Wiley & Sons, Inc., New York, 1949, particularly pages 18 and 19.) High thermal stability is important in a liquid monopropellant since it is desirable to use the monopropellant itself as a coolant in a regeneratively cooled rocket engine system. In such applications, the monopropellant may be heated, e.g., to average temperatures of 300 F. and higher, and should be able to withstand such temperatures without thermal decomposition. Good storage stability is obviously desirable, and it is also desirable that the monopropellant be relatively nonvolatile and non-corrosive in character so that it can be handled without special precautions.

According to the present invention, it has been found that the new compound 2,Z-diiluoro-2-nitroethano1, CF NO CH OH, possesses all the above desired properties to a high degree. It has a high specific impulse of 241 pounds per second per pound. It shows no significant decomposition when heated for long periods at a temperature of about 400 F. It is a relatively non-volatile liquid having excellent storage stability. It is essentially non-corrosive with respect to all ordinary materials of construction such as metals and glass, many plastics and thus can be stored and handled without special precautions.

The desirable properties of CF NO CH OH as a monopropellant are apparent when this compound is compared on the basis of specific impulse, thermal stability, storage stability and ease of handling with other typical monopropellants. In Table I, such a comparison is shown between CF NO CH OH and four well-known monoconditions.

and exhaust, respectively, of 1000 p.s.i. and 14.7 p.s.i. The determination was made according to the method described in Thermodynamics of High Temperature Gas Mixtures and Application to Combustion Problems, by John S. Gordon, PB 133980, US. Govt. Research Reports, November 14, 1958.

CF NO CH OH may be prepared by the addition of dinitrogen tetroxide to 1,1-difluoroethylene (CH CF to form a nitro-nitrite addition product which may be converted by alkaline hydrolysis to the nitroalcohol. The reaction is believed to proceed as follows:

The reaction is desirably carried out in the presence of a solvent which is unreactive to N 0 under the reaction Without a solvent, the addition reaction is difiicult to control, and explosion may occur. Preferred are the halogenated solvents, particularly the chlorinated or chlorofluorinated solvents such as chloroform, methylene chloride (CH Cl carbon tetrachloride, trichlorotrifluoroethane, dichlorotetrafiuoroethane, etc. The amount of solvent is not critical and generally may be used in an amount ranging from to 1000 milliliters per mole of olefin. Desirably the reaction is carried out under substantially anhydrous conditions to avoid reactions between N 0 and water and the possibility of other side reactions.

Preferably the reaction is carried out under moderate pressures of, e.g., 100 to 2,000 lbs/in. and at moderate temperatures of, e.g., 20 C. to 100 C. Approximately equimolar amounts of 1,1-difluoroethylene and dinitrogentetroxide are usually employed. Following the formation of the dinitrogen tetroxide addition product by the above procedure, the addition product is hydrolyzed, preferably using a weak aqueous alkaline solution, such as a sodium bicarbonate solution, and the hydrolysis product CF NO CH OH then isolated by decantation of the organic portion and extraction with ether or other suitable solvent of the aqueous portion, and vacuum distillation.

The following example illustrates the preparation of CF NO CH OH by the above procedure.

Example 1 A stainless steel autoclave of 1 liter capacity is charged with grams of dinitrogen tetroxide dissolved in 500 grams of CClF CCl F at 0 C. after which grams of CH CF is introduced by vacuum transfer with the propellants. 50 autoclave cooled in liquid nitrogen. The sealed auto- TABLE I Specific impulse, Thermal stability Storage stability Ease of handling 1b./sec./lb.

2,Z-difiuoro-Z-nitroethane 241 Stable on heating for Stable indefinitely Not highly flammable. Stores 8 hrs. at 200 C. under normal storas aliquid at normal pressure (392 F.). age conditions. and temperature in conventional container.

Amine nitrates in nitric acid 256 Deeomposes above Stable if stored in acid Highly corrosive, strong oxidiz- 25 proof containers. ing agent.

H d i 221 Unstable over 200 F Stable only when Moderately toxic, highly instored under rigidly flammable, subject to catalytic gontrolled condiviolent decomposition.

ions.

Eth p id 198 do Must be stabilized to Must be stored under pressure,

prevent polymerihighly inflammable. May zation. polymerize violently.

Hydrogen peroxide do Slow, spontaneous Severe explosion hazard. Ignites decomposition on most combustible materials storage. on contact.

The ideal specific impulse (in pounds of thrust delivered at a propellant flow rate of one pound per second) was determined for conditions of shifting equilibrium during expansion and for a pressure in the combustion chamber clave is then placed on a mechanical shaker and allowed to warm to room temperature. An exothermic reaction ensues causing a temperature increase to about 90 C. and a pressure increase to 900 lbs./in. Agitation is continued for 8 hours during which time the autoclave cools to 30 C.' and the pressure decreases to 500 lbs/m The autoclave is vented and the liquid contents poured into an equal volume of water to which is added, with stirring, a sodium bicarbonate solution until neutralized. The organic layer is separated and dried over anhydrous magnesium sulfate and after removal of CClF CCl F by distillation 10 grams of a pale yellow oil is obtained the middle cut of which, boiling at 47 C. at about 12 mm. Hg, is the nitro alcohol CF NO CH OH. The infrared spectrum of this compound shows the characteristic OH band at 2.99 1 (bonded); the characteristic N band at 6.3;; and carbon-fluorine stretching vibrations, at 8-10;/.. The aqueous layer is acidified and then extracted three times with diethyl ether, the ether solution dried and evaporated to give 25 grams of a red oil, which on vacuum distillation, is shown to consist of mostly CF NO CH OH. A middle cut boils at 63 C. at about 20 mm. Hg. The N-phenyl carbamate ester of the 2,2-difiuoro-2-nitroethanol is prepared with phenyl isocyanate using triethyl amine as a catalyst. Recrystallization of the ester (NO CF COOH) The precursor compound NO CF COOH can be readily prepared by the reaction of N 0 with tetrafluoroethylene followed by hydrolysis of the addition product in accordance with the following:

Reduction of the acid may be accomplished in various ways such as with diborane formed in situ by the reaction of boron trifluoride etherate with sodium borohydride.

We claim:

The compound 2,2-difluoro-2-nitroethanol.

No references cited.

LEON ZITVER, Primary Examiner.

LEON D. ROSDOL, Examiner. 

